Mendel suggested that flower colour was controlled by inherited factors. Draw a ring around the correct answer to complete the following sentences.

Transcription

1 Q. The diagrams show one of Mendel s experiments. He bred pea plants. Mendel suggested that flower colour was controlled by inherited factors. Draw a ring around the correct answer to complete the following sentences. (a) The first generation plants show that the red factor is dominant. environmental. recessive. () (b) The second generation plants show that the white factor is dominant. environmental. recessive. () (c) What do we call inherited factors?... () Page of 3

2 (d) How are inherited factors passed from generation to generation?... () (Total 4 marks) Q2. (a) How many pairs of chromosomes are there in a body cell of a human baby? () (b) Place the following in order of size, starting with the smallest, by writing numbers 4 in the boxes underneath the words. () (c) For a baby to grow, its cells must develop in a number of ways. Explain how each of the following is part of the growth process of a baby. (i) Cell enlargement... () (ii) The process of cell division by mitosis (3) (d) Why is cell specialisation (differentiation) important for the development and growth of a healthy baby from a fertilised egg? (2) (Total 8 marks) Page 2 of 3

3 Q3. (a) Sex cells are produced by meiosis. Describe what happens to the chromosomes when a cell divides by meiosis. (2) (b) Darwin s theory of natural selection depends on the fact that individual organisms within a species may show a wide range of variation. Explain how meiosis and sexual reproduction give rise to variation. (2) (c) Mutation may also give rise to variation. (i) What is meant by mutation? () (ii) Are all mutations harmful? Explain the reason for your answer. (2) (Total 7 marks) Page 3 of 3

4 Q4. Sometimes babies are born with extra fingers or toes as shown in the photograph. This condition is called polydactyly. CNRI / SCIENCE PHOTO LIBRARY The diagram shows the inheritance of polydactyly in a family. (a) Polydactyly is caused by a dominant allele, D. The recessive allele of the gene is represented by d. Use one genetic diagram to show the inheritance of the polydactyly gene by R and S. (4) Page 4 of 3

5 (b) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. Embryos can be screened for genetic disorders. Many people would favour the use of embryo screening for cystic fibrosis but not for polydactyly. Compare the issues involved in the use of embryo screening for cystic fibrosis and for polydactyly. You should use your knowledge and understanding of the process and the two conditions (6) (Total 0 marks) Page 5 of 3

6 Q5. The drawing shows some of the stages of reproduction in horses. (a) (i) Name this type of reproduction... (ii) Name the type of cell labelled A... () () (b) Name the type of cell division taking place at the stage labelled: (i) B... (ii) C... (2) (c) How does the number of chromosomes in each cell of the embryo compare with the number of chromosomes in cell A? () (d) When the foal grows up it will look similar to its parents but it will not be identical to either parent. (i) Explain why it will look similar to its parents. () Page 6 of 3

7 (ii) Explain why it will not be identical to either of its parents. (2) (Total 8 marks) Q6. A woman gives birth to triplets. Two of the triplets are boys and the third is a girl. The triplets developed from two egg cells released from the ovary at the same time. The diagram shows how triplets A, B and C developed. (a) Which stages on the diagram show gametes? Draw a ring around your answer. and 2 2 and 3 3 and 7 and 7 () Page 7 of 3

8 (b) Embryo B is male. Which of the following explains why embryo B is male? Tick ( ) one box. Cell P has an X chromosome; cell R has an X chromosome. Cell P has a Y chromosome; cell R has an X chromosome. Cell P has an X chromosome; cell R has a Y chromosome. () (c) The children that develop from embryos A and C will not be identical. Explain why. You may use words from the box in your answer. egg genes sperm (2) (d) Single cells from an embryo at Stage 7 can be separated and grown in a special solution. (i) What term describes cells that are grown in this way? Draw a ring around your answer. lleles screened cells stem cells () Page 8 of 3

9 (ii) What happens when the cells are placed in the special solution? Tick ( ) two boxes. The cells divide The cells fertilise The cells differentiate The cells separate (2) (iii) Give one use of cells grown in this way. () (iv) Some people might object to using cells from embryos in this way. Give one reason why. () (Total 9 marks) Page 9 of 3

10 Q7. The diagram shows a spider plant during one type of reproduction. Complete the sentences using words from the box. asexual characteristics chromosomes gametes genes mitosis sexual (a) The colour and shape of the leaves of a spider plant are known as... (b) The shape of the leaves is controlled by... () () (c) The thread-like structures inside the nucleus of the cells are called... () (d) The spider plant produces new cells in the runner by a process called... () (e) This type of reproduction is called... reproduction. () (Total 5 marks) Page 0 of 3

11 Q8. The diagram shows one of the experiments performed by a scientist called Mendel in the 850s. He bred pea plants which had different coloured pea seeds. (a) Use words from the box to help you to explain the results of this experiment. dominant factor recessive (3) (b) Mendel explained these results in terms of inherited factors. (i) What do we now call inherited factors? () (ii) Where, in a cell, are these inherited factors found? () (Total 5 marks) Page of 3

12 Q9. In the 850s, Gregor Mendel carried out breeding experiments using peas. (a) The importance of Mendel s work was not recognised until the early 900s. Explain why. (2) (b) A student repeated one of Mendel s experiments. The flow chart shows her procedure. The diagram shows a representative sample of seeds produced by second generation plants. Page 2 of 3

13 (i) Describe how the student could obtain a sample that is representative of seeds produced by the second generation. () (ii) What was the approximate ratio of yellow seeds to green seeds in the seeds produced by the second generation? () (iii) Seed colour in peas is controlled by a single gene which has two alleles. Use a genetic diagram to show why this ratio of yellow seeds to green seeds was produced by the second generation. Use the symbol A to represent the dominant allele, and a to represent the recessive allele. (4) (Total 8 marks) Q0. Complete each sentence by choosing the correct terms from the box ADH DNA XX XY YY dominant female male recessive strong weak A gene is made up of a substance called.... Genes are found on chromosomes and most human cells contain... pairs of chromosomes. In females the two sex chromosomes are..., but in males the two sex chromosomes are.... Alleles are alternative forms of a gene. Two healthy parents can sometimes have a child with a genetic disorder such as cystic fibrosis. This is because cystic fibrosis is caused by a... allele. The two parents are healthy because they also have the... allele. (Total 6 marks) Page 3 of 3

14 Q. The diagram shows two patterns of cell division. Cell division type A is used in gamete formation. Cell division type B is used in normal growth. (a) Name the two types of cell division, A and B, shown in the diagram. Type A... Type B... (2) (b) Name the process in which an egg and sperm join together. () (c) Cell contains 46 chromosomes. How many chromosomes will there be in: (i) cell 0;... () (ii) cell 4?... () (Total 5 marks) Page 4 of 3

15 Q2. The diagrams show four ways in which human twins may be formed. Which diagram, A, B, C or D, shows the process which will produce genetically identical twin boys?... Explain the reason for your choice (Total 3 marks) Page 5 of 3

16 Q3. (a) Mice with black fur can have the genotype BB or Bb, whilst mice with brown fur have the genotype bb. (i) Use a genetic diagram to show what fur colours you would predict in the F offspring produced by two mice who are both Bb. (3) (ii) Why might your prediction of fur colour in the F generation not be proved right? () (b) Using the example in part (a) to help: (i) describe the difference between dominant and recessive alleles; (2) (ii) describe the difference between alleles and genes; (2) Page 6 of 3

17 (iii) describe the difference between homozygous and heterozygous chromosomes. (2) (Total 0 marks) Q4. Meiosis and mitosis are different types of division in human cells. Compare the two processes by referring to where each takes place and the kind of products that are made (Total 6 marks) Page 7 of 3

18 Q5. Cystic fibrosis is an inherited disease which causes the tubes in the lungs to be blocked with sticky mucus. Two parents who do not have the disease can still produce children who do have the disease. (a) Explain how children can inherit this disease from parents who do not have it (use a genetic diagram in your answer if you want to). (4) (b) Mucus contains protein. The information for the production of this protein is stored in a gene. Explain how a change in a gene causes a different protein to be produced. (3) (Total 7 marks) Page 8 of 3

19 M. (a) dominant (b) recessive (c) genes (d) gametes [4] M2. (a) 23 (b) chromosome nucleus gene cell (c) (i) any one from (cells which are bigger) take up more space (ii) (cells) have to get bigger or mature to divide chromosomes duplicate or make exact copies of self accept forms pairs of chromatids nuclei divide accept chromatids or chromosomes separate identical (daughter) cells formed accept for example, skin cells make more skin cells or cells are clones (d) any two from Differentiation mark babies need or are made of different types of cells or cells that have different functions accept different cells are needed for different organs Page 9 of 3

20 Division or specialisation mark as fertilised egg starts to divide each cell specialises to form a part of the body accept specialised cells make different parts of the body Growth mark specialised cells undergo mitosis to grow further cells accept cells divide or reproduce to form identical cells 2 [8] M3. (a) any two from copies of chromosomes made cell divides twice or 4 cells formed each gamete / cell now has single set of chromosomes allow chromosome number halved / cells haploid / cells n 2 (b) any two from sex cells / gametes fuse / fertilisation offspring receive genes or chromosomes or alleles from both parents / DNA alleles in a pair may vary 2 Page 20 of 3

21 (c) (i) new form of gene allow change in genetic material / DNA / chromosomes / gene (ii) (no) any two from some neutral exemplified e.g. extra digit some increase chances of survival / reference to natural selection or evolution exemplified e.g. example of disease resistance 2 [7] M4. (a) (genotype / gametes from P / father) D and d (*) (genotype / gametes from Q / mother) d and d / accept d(*) offspring genotypes correctly derived from correct gametes(*) offspring phenotypes R and S identified (*) eg may be in punnett square allow own upper and lower case symbols or allow any symbol correctly used with key (b) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. No relevant content. There is a brief description of the issues involved in screening for at least one condition. There is some description of issues involved in screening for both conditions but there is a lack of both pros and cons for the two conditions. There is a clear, balanced and detailed description of the issues involved in screening for both conditions, giving pros and cons for each condition. 0 marks Level ( 2 marks) Level 2 (3 4 marks) Level 3 (5 6 marks) Page 2 of 3

22 examples of biology points made in the response For cystic fibrosis pros: reduce number of people with cystic fibrosis (in population) reduce health-care costs allows decision / emotional argument, eg allows people to make choices about termination cons: possible damage / risk to embryo / fetus / baby possible harm / risk to mother (may) have to make ethical / moral / religious decisions for polydactyly: cures disfigurement but condition not life threatening so risks to foetus / mother unjustified [0] M5. (a) (i) sexual / sex (ii) egg / gamete / sex cell / ovum (reject ovule) for mark each 2 (b) (i) meiosis / reduction (ii) mitosis / somatic for mark each 2 (c) twice as many (reject answers based on 23 / 46 chromosomes) for one mark (d) (i) information / genes / DNA passed from parents (chromosomes neutral) for one mark Page 22 of 3

23 (ii) genes / genetic information / chromosomes from two parents alleles may be different environmental effect / named may have been mutation any two for mark each 2 [8] M6. (a) 2 and 3 (b) (c) cell P has an X chromosome; cell R has a Y chromosome any two from: (formed from) different egg / 2 eggs (formed from) different sperm / 2 sperm have different genes / alleles / chromosomes / DNA allow genetics 2 (d) (i) stem cells (ii) (iii) (iv) the cells divide the cells differentiate (medical) research / named eg growing organs or medical / patient treatment allow (embryo) cloning do not allow designer babies / more babies any one from: ethical / moral / religious objections ignore cruel / not natural / playing God potential harm to embryo allow deformed ignore harm to mother [9] Page 23 of 3

24 M7. (a) characteristics (b) genes (c) chromosomes (d) mitosis (e) asexual [5] - M8. (a) any three from: factor for colour has two forms accept gene for factor and allele for form yellow dominant since all first generation yellow accept F for first generation green recessive since reappears in second generation accept F2 for second generation (b) (i) genes accept alleles / genetic 3 (ii) nucleus accept chromosomes / DNA [5] Page 24 of 3

25 M9. (a) any two from: accept other logical / reasonable ideas other scientists not aware of his work chromosomes / DNA / genes not seen / discovered / known do not accept there was no interest in genetics other theories accepted at the time not considered to be a scientist / not eminent / respected allow he was just / only a monk 2 (b) (i) random selection accept a method of achieving random selection eg take a handful if number given, minimum 20 (ii) any one from: : / one to one 9:2 accept any ratio to give correct answer, eg 50:50 do not accept 2:9 unqualified (iii) A + a as gametes from st parent a + a as gametes from 2nd parent allow a alone (offspring / 2 nd generation) Aa aa offspring must be derived from correct gametes correct identification of yellow (Aa) other symbols correctly used can gain full marks or green (aa) (if both given, both must be correct) ignore references to previous generations if no other marks awarded, both correct parental genotypes given gains mark Page 25 of 3

26 examples of award of first three marks [8] M0. in the correct order DNA 23 XX XY recessive dominant [6] Page 26 of 3

27 M. (a) A = meiosis accept mieosis do not accept miosis B = mitosis do not accept meitosis etc (b) fertilisation allow conception (c) (i) 23 (ii) 46 [5] M2. D idea that twins have come from one (fertilised) egg idea that Y sperm / Y chromosome produces boys each for mark allow mark if candidate selects A and states that Y sperm / Y chromosome produce boys (reject Y gene unqualified) OR allow mark if candidate selects C and states that twins must have come from one (fertilised) egg [3] M3. (a) (i) gametes i.e. B b and B b correct combination of genotypes i.e. BB, Bb, Bb, bb correct analysis of phenotypes i.e. 3 black fur with brown fur (ii) award one mark for the recognition that it is down to chance (which two gametes fuse) and not simply because it s a prediction do not accept mutation (b) (i) B is dominant/ an allele is dominant if it is expressed in the heterozygous phenotype candidates are likely to use a variety of ways of expressing their ideas Page 27 of 3

28 (ii) b is recessive/ a recessive allele is not expressed in the presence of its contrasting allele do not accept powerful do not accept stronger alleles are different forms of a gene controlling a characteristic and occupying the same site on homologous chromosomes (e.g. B or b) genes are the units of DNA/sites on chromosomes carrying the information that determines characteristics (e.g. bb) (c) homozygous: BB / bb / possessing a pair of identical alleles for a character/true breeding give credit to an explanation using a diagram heterozygous: Bb / carrying a pair of contrasting/different alleles for a characteristic do not accept references to xx, xy do not accept gene by itself [0] Page 28 of 3

29 M4. one mark for each of the following comparisons to a maximum of 6 candidates must make a clear comparison meiosis sexual gametes ovary or testes or gonads half number of chromsomes mitosis asexual growth all other cells same number of chromosomes haploid or diploid or 23 chromosomes 46 chromosomes reassortment or variation possible or not identical no reassortment or no variation or identical 4 cells produced 2 cells produced 2 divisions division [6] M5. (a) caused by a recessive* gene / allele (allow non / not dominant) both parents heterozygous / carry the gene / allele for mark each offspring needs two recessive genes to have / inherit disease for 2 marks or Nn Nn NN Nn Nn nn for mark each nn identified as having the disease* for 2 marks 4 Page 29 of 3

30 (b) any reference to DNA gains mark but different genes means difference in DNA gains 2 marks idea of different codes / instructions for making proteins or different (order of) amino acids (in proteins) for mark 3 [7] Page 30 of 3

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